Just to make things even clearer...
On Sep 20, 2012, at 02:22 , Gregg Kellogg wrote:
> I've prepared an updated Microdata to RDF Working Draft for review [1]. Please note that, as this is a Note of the Semantic Web Interest Group, and the HTML Data Task Force is complete, the official place for feedback is semantic-web@w3.org.
>
> This update adds support for vocabulary expansion, principally to support features such as schema:additionalType. Microdata vocabulary expansion is a subset of RDFa vocabulary expansion, and is fully compatible with RDFa, such that toolsets which process both RDFa 1.1 and Microdata to RDF can use a single vocabulary expansion algorithm, although its use in Microdata is mandatory, whereas it is optional in RDFa 1.1.
>
> To support vocabulary expansion, additional features are added to the registry: within a vocabulary, a property can be either specified as "equivalentProperty" of another IRI, or "subPropertyOf" another IRI, to use either owl:equivalentProperty or rdfs:subPropertyOf expansion rules. The default registry has been updated for additionalType as follows:
>
> {
> "http://schema.org/": {
> ...
> "properties": {
> "additionalType": {"subPropertyOf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#type"}
> ...
> }
> }
>
> Note that the current published registry [2] has not been updated. The version of the registry used for this working draft is available in the supplement [3], and in the mercurial repository [4].
>
> Additionally, when a vocabulary is detected, an rdfa:usesVocabulary triple is generated, which enables the RDFa 1.1 vocabulary expansion toolchain. If at some point schema.org includes OWL2 expansion rules supported by RDFa within the vocabulary definition, this will allow full use of this through RDFa tool chains which support Microdata to RDF.
>
To emphasize: the microdata->RDF does not _require_ to perform this extra step; the only reason of adding this extra statement is to allow toolchains to be used for the purpose if they are prepared for it.
Ivan
> The draft references the test-suite [5], which now has a number of tests (currently 74) available to help developers check processor conformance. This includes all of the current schema.org microdata examples.
>
> After a reasonable feedback period, this working draft will update the current published note [6].
>
> Thanks to Ivan for invaluable help in preparing this update.
>
> Gregg Kellogg
> gregg@greggkellogg.net
>
> [1] http://dvcs.w3.org/hg/htmldata/raw-file/default/ED/microdata-rdf/20120919/
> [2] http://www.w3.org/ns/md
> [3] https://dvcs.w3.org/hg/htmldata/raw-file/default/microdata-supplement/index.html
> [4] https://dvcs.w3.org/hg/htmldata/raw-file/default/microdata-namespace/ns.json
> [5] http://dvcs.w3.org/hg/htmldata/raw-file/default/microdata-rdf/tests/
> [6] http://www.w3.org/TR/2012/NOTE-microdata-rdf-20120308/
----
Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
FOAF: http://www.ivan-herman.net/foaf.rdf